The present invention relates to an acoustic fluid machine to keep temperature gradient as small as possible between the base having an actuator for an acoustic resonator and the top end having a valve device for sucking and discharge.
Japanese Patent Pub. No. 2004-116309A corresponding to U.S. patent application Ser. No. 10/922,383 filed Aug. 19, 2004 discloses an acoustic fluid machine in which an actuator that has a piston is provided at the base of a tapered acoustic resonator for creating in-tube wave motion with acoustic resonation, and a valve device for sucking and discharging fluid with pressure fluctuation therein.
In the acoustic fluid machine, only when fluid temperature is within a certain range, the shape and size of the acoustic resonator enables the optimum resonation frequency to be produced, thereby carrying out the optimum sucking and discharge of the fluid. Should resonation frequency be out of the predetermined range, compression ratio becomes smaller, making it impossible to obtain a desired discharge pressure.
The resonation frequency varies with change in temperature of the resonator. Thus, calculation of the resonation frequency allows frequency of the actuator of the piston to vary to match the calculated resonation frequency thereby exhibiting a desired sucking/discharge.
Accordingly, it is necessary to use arithmetic equipment to control the actuator of the piston, which makes its structure complicate and involves high cost.
Temperature in the acoustic resonator of the acoustic fluid machine is high at the generally-closed top end or a valve device, while it is low at the generally-opening piston and actuator therefor to increase temperature gradient. If temperature gradient in the acoustic resonator is as small as possible, the determined resonation frequency will be within a normal compression area without deviation or with slight deviation.